Recently, a transfer device for transferring a coating film onto a transfer-receiving object such as paper has been widely used because of its advantageous feature of easy handling for supplying an adequate amount as a replacement for touch-up liquid and liquid paste. A transfer device applying a white correction film for touch-up makes a correction by transferring the correction film onto a correction point of a transfer-receiving object. A transfer device employing an adhesive film for adhesively connects the transfer-receiving object and an attachment substance fixes the attachment substance to the adhesive film transferred onto the transfer-receiving object.
Both types of the above-described transfer devices have similar structures except for the coating film used which is adhesive or white. More specifically, such a transfer device includes a feed shaft unit, a roll up shaft unit and a transfer unit within a casing. The feed shaft unit rotates to supply band-shaped ribbon coated with a coating film. The roll up shaft unit rotates to wind up the band-shaped ribbon after transferring the coating film onto a transfer-receiving object.
The roll up shaft unit and the feed shaft unit engage with each other by means of, for example, gears, and thus the roll up shaft unit rotates in accordance with the revolution of the feed shaft unit while the band-shaped ribbon is being supplied. The transfer unit is disposed projecting from an opening formed at an end of the casing. The transfer unit pulls out the band-shaped ribbon coated with coating film from the feed shaft unit, transfers the coating film onto the transfer-receiving object, and then sends the band-shaped ribbon to the roll up shaft unit.
In the transfer device of this type, malfunction occurs if the tension of the band-shaped ribbon in the region between the feed shaft unit and the roll up shaft unit (hereinafter referred to as “tension”) is too high or too low. More specifically, when the tension is too low, the band-shaped ribbon may be loosened and the feed shaft unit may fail to rotate engagedly with the roll up shaft unit. Reversely, when the tension is too high, an additional force is required for supplying or winding up the band-shaped ribbon (hereinafter referred to as “traveling”) is required and in an extreme case the band-shaped ribbon is broken up.
To cope with this problem, the feeding rotation of the feed shaft unit in a typical transfer device is loaded so as to prevent at least extreme lowering of the tension (hereinafter referred to as “braking force”). This method, however, has a following drawback, as the braking force is kept constant from the beginning till the end of operation.
At the initial period of operation, the traveling is smooth as the rolling diameter of the feed shaft unit is large. At the end of operation, however, the tension of the band-shaped ribbon is higher compared with the standard tension during the normal traveling at the start, since the roll diameter of the feed shaft unit becomes smaller at the end than the roll diameter of the feed shaft unit at the start, which makes the traveling to be heavy.
Such a tension fluctuation of the band-shaped ribbon from the beginning till the end of operation deteriorates the maneuverability of the transfer device for the user, making handling of the device to be difficult. Thus, it is required to maintain a constant tension of the band-shaped ribbon from the beginning till the end of operation for improving the maneuverability.
An example of a transfer device in which the tension of the band-shaped ribbon is kept constant has been proposed in Japanese laid-open patent publication No. 9-71097, having the following structure. A supply reel collar (feed shaft unit) having an L-shaped section is disposed on an upper surface of a supply gear opposite to the gear in the direction of the shaft center. A spring is wound around the shaft center of the supply gear within the space between the L-shaped section of the supply reel collar and the shaft center of the gear.
A pressing plate is fittingly provided around the shaft center of the supply gear to contact with the spring at the side opposite to the side at which the spring contacts with the supply gear and to slide along the shaft center of the supply gear. Further, a female screw is formed at the upper inside of the shaft center of the supply gear, into which screw a variable button is threaded.
According to the structure of the transfer device disclosed in above Japanese laid-open patent publication No. 9-71097, the user adjusts the tension of the band-shaped ribbon by screwing the variable button into and out of the shaft center of the supply gear appropriately and arbitrarily. In other words, the user alters the interval between the pressing plate and the supply gear by operating the variable button during use.
When the interval is decreased by controlling the variable button, the supply reel collar is allowed to press the surface of the supply gear by the force of the spring. The braking force is simultaneously applied to the rotation of the supply reel collar. When the interval is increased by operating the variable button, the above braking force is reduced leaving a predetermined amount of the spring force applied.
However, according to the structure of Japanese laid-open patent publication No. 9-71097 described as above in which the tension of the band-shaped ribbon can be varied, the user is required to manipulate the variable button appropriately, which requirement forced on the user deteriorates the convenient feature of the transfer device. Moreover, since the user is not particularly conscious of the relationship between the amount of use and the tension of the band-shaped ribbon, it is extremely difficult to actually keep the tension of the band-shaped ribbon constant.
The object of the present invention is to solve the above problem, providing a transfer device capable of maintaining a constant tension of a band-shaped ribbon from the beginning till the end of operation requiring no action by a user.